Various collapsible members have been used to form beams for collapsible structures such as temporary buildings and tents and also for work arms to position working tools in awkward locations. The collapsible structural members typically employ cables as tensioning members to bring separate segments or modules together to form a rigid structure. Such prior art structures usually rely on the cable itself to provide rigidity to the member or to separate pins or fasteners which must be installed to obtain rigidity and must be removed to permit collapse of the structure. Usually collapsible structural members require multiple parts and also require substantial time to form a structure and to collapse that structure.
There is a need for a collapsible structural member which is simple to erect and to collapse and uses a minimum number of parts. It appears also that there is a need for a collapsible structural member which uses a tensioning member to bring the parts together but which locks them in a position so that they are not reliant on the tensioning member for rigidity or strength.
An object of the invention is to provide a collapsible structural member which is simple and eliminates the need for many removable parts.
Another object of the invention is to provide a collapsible structure member where a tensioning member is used to bring components, segments or modules of the structure together and into a position in which the components lock together frictionally and are maintained in the locked position without undue loading required on the tensioning member.
A further object of the invention is to provide a collapsible beam structure which uses frictional locking principles similar to that used in Morse tapers for locking tapered drill bits and complementary tapered rotatable chucks to provide frictional locking between the drill and the chuck to transmit rotational torque.
Still another object of the invention is to provide a collapsible beam structure having the ability of locking adjacent modules relative to each other using complementary spherical locking surfaces to provide a frictional lock required to hold the modules in a rigid position relative to each other whether the modules are aligned axially or at an angle to each and independently of the cable or tensioning member.